In lithography processes for recording media like flash memories, and semiconductor elements that form a Central Processing Unit (CPU), an original pattern formed in a mask is transferred to a wafer that will be the substrate of a semiconductor element. The original pattern is formed in the mask by, for example, an electron beam lithography system.
In recent years, in view of the accomplishment of an improved throughput, multi-beam type electron beam lithography systems capable of forming a pattern using multiple electron beams are introduced in industries. Such electron beam lithography systems cause electron beam emitted from a single electron source to pass through an aperture formed with multiple openings, and thus the electron beam is split to multiple beams. Hence, each electron beam has variabilities in the spot shape and the dose amount in accordance with the process precision of the aperture.
The dose amount of electron beam is controllable to some level by, for example, adjusting the exposure time. When, however, in view of the increase in number of electron beams applied for lithography in future, it is expected that a precise pattern formation becomes difficult by simply controlling the dose amount of electron beam. Hence, in order to form a precise pattern, it is necessary to selectively utilize an aperture that has little variability in opening shape, and to precisely split electron beam at first.